A major effort will be made to complete the studies on 1. the total daily fluoride intake of infant-toddlers and adults based on the analysis of the "food groups" collected by the F.D.A. in four regional areas, 2. the effect of fluoride on lipid metabolism in isolated osteoblasts, 3. the rates of bone formation and resorption in calcium deficient lactating rats, 4. the role of fluoride in vitro and in vivo on iron transport through membranes, 5. the toxicology and metabolic handling of perfluorooctanoic acid in rats and 6. the effect of fluoride on the urinary excretion of cAMP. Radioimmunoassay technique for PTH will be employed to initiate studies to determine the effect of fluoride and magnesium deficiency on the level of circulating PTH. In addition, investigations of the effect of 1. fluoride on bone metabolism of zinc deficient rats, 2. fluoride intake and vitamin A on glycosaminoglycans metabolism in calcified tissue, 3. fluoride intake on levels of vitamin E in Serum and selected tissues and 4. the in vivo stabilization of the amorphous fraction of bone mineral by magnesium are to be initiated. Investigations of the effect of aluminum in water on assimilation, distribution and retention of fluoride are also to be pursued.